Flushing fluid for hydraulic



Patented May 3, 1949 UNITED STATES ATENT OFFICE FLUSHING FLUID FOR HYDRAULIC BRAKE SYSTEMS Chester M. White, Rochester, N. Y., assignor to Genesee Research Corporation, Rochester N. Y., a corporation of New York No Drawing. Application September 7, 1945, Serial No. 615,078

the most effective, and as explained hereinafter, it is desirable that these alcohols be substantially anhydrous. Methyl alcohol is the most desirable because of its low viscosity and specific gravity position useful in the flushing or purging of 5 and because of its eiflciency in penetration of deteriorated brake fluids from hydraulic brake gumined or oxidized castor oil. Low specific systems. More specifically, the invention congravity and viscosity make for added turbulence templates and provides a novel flushing fluid of of flow, under pressure bleeding of the hydraulic the foregoing character which not only possesses system, which results in enhanced washing action. markedly improved solvent action on brake fluid Efficiency in penetration aids in loosening or deterioration products tending to accumulate on softening the gum deposits. Ethyl alcohol as well the metal and rubber surfaces of the hydraulic as propyl alcohol may be substituted for the brake system but which also will not corrode the methyl alcohol but, in the case of ethyl alcohol, metal surfaces and cause the rubber parts to denaturants such as petroleum derivatives must swell. Likewise encompassed Within the scope of not be used because of the deteriorating tenthe invention is an improved process for flushing dencies hereinbefore referred to. Butyl alcohol is hydraulic brake systems employing the novel not preferred because of its known property of flushing fluid herein described and claimed. attacking rubber.

Most hydraulic brake fluids in use at the The aliphatic alcohol solvent is the major conpresent time comprise as their principal constitstituent of the improved flushing fluid and should uents castor oil and a solvent therefor. As is be present to the extent of at least about 70% well known, castor oil has a tendency to oxidize oi the composition. The other components of the and, in time, because of this tendency and also fluid are present in only comparatively minor perb'e ause 0 the tend n y o t e So ent &0 e DO- centages as will appear more particularly hereinrate, hydraulic brake fluids made up of castor oil after. if and solvent in n viscosity to s h n e a very important feature of the invention is the tent that the brake system becomes less sensidiscovery th t t v t action of 'lower tive and response to brake pedal act COIISB- aliphatic alcohol solvents on deterioration prodfl t y W l Because of this ucts of hydraulic brake fluids may be enhanced deierlqmilon, 1t 15 advlsable flush the system and markedly increased by incorporating with the ggg i ez f jge sig l z i e gi'zi gflfig g rgg alcohol a comparatively small amount of a ma- & e l terial herein described as a solvent-action pro- 2 i flf g f i ggig fi gi yg ggfi g t moter. The theory of action of this promoter is k Q .i All S a --.-n freeze alcohol or completely denatured alcohol, 22 3 2 5 i gs g zgg zgg hve en ldllCi r'h' .Te i

1 3 g ifif g g g sg i ifi n1 the1 sense thattthe final improved solvent ents which are detrimental to brake parts. For ion 15 ue merely. 0 the addl'tl Solvent action of each material. Stated dlfierently, the instance, gasoline and light mineral oils are in cm arafivel small amount f rom ter m common use as denaturants in completely de- 40. p y 9 p 0 e natured alcohol and as evaporation retarders in ployed causes an Increment of Increased solvlant antifreeze alcohol. These materials are most actlon of far greater magnitude i that Whlch undesirable in hydraulic brake system flushing could be caused any Solvent action possessed because of their very vigorous deteriorating acby the promoter Itself tion on rubber piston cups which manifests itself 40 Preferred solventactlon promofiers are cycltc in inordinate swelling alcohols which may be heterocycllc, carbocychc The non-corrosive and improved solvent-action or nymocarbfocychc' Typ1ca1 of these materla'ls flushing fluid of the present invention comprises, found opera/V6 for this purpose are furfuryl alco as its essential ingredients, (1) an organic solhol, cyclohexanol, alpha terpmol, benzyl alcohol vent, and (2) a so1vent acti0n promoter thymol, cresol (USP), 1,3,5 Xylenol, phenol (40 sira'oly, the composition also contains an anticorrosive agent and water.

.As the organic solvent, lower straight chain aliphatic alcohols containing less than four carbon atoms in the chain have been found to be M. P.), and catechol. Employed in the final flushing composition in proportions of from. 1 to 20%, these promoters not only perform their disclosed function but are by actual test sub-- stantially non-corrosive-to metals suchas alumi- 3 num alloys, brass and iron, as well as substantially non-deleterious toward rubber.

Since the aliphatic alcohol solvent of the present flushing fluid composition has in and of itself a slight tendency to cause corrosion of iron and brass parts, it has been found advisable to include in the composition a comparatively small amount (1 to 5%) of an anti-corrosive agent. Cyclic amines, themselves non-corrosive to metals in the dilution indicated, are suitable for this purpose. Typical cyclic amines are: morpholine, methyl morpholine, ethyl morpholine, pipyridine, cyclohexylamine, dicyclohexylamine, benzothiazol, pyridine and aniline.

Aside from performing the function of cutting down corrosive action of the aliphatic alcohol solvent, these cyclic amines, surprisingly enough, likewise exhibit to a certain extent the power of promoting solvent action of the alohol in the sense described hereinbefore. They therefore perform a dual function in the composition.

Completely anhydrous lower aliphatic alcohol solvents themselves react slowly with aluminum and, to overcome this corrosive effect, a small amount of water may be added to the composition. There is a limit, however, as to the amount of water which may be added since the presence of too much water will impair the rate of turbulence of flow and the efficiency of the composition in penetrating gummed or oxidized oils. The water content should be kept below approximately 5.0% for optimum results.

In general, and by way of recapitulation, the components of the improved flushing fluid are employed in the following approximate proportions:

Per cent Organic solvent 96.0 to 73.0 Solvent-action promoter 1.5 to 20.0 Anti-corrosive agent 1.5 to 5.0 Water 1.0 to 2.0

The following specific formulae have been found to be particularly eiiicient:

Example A Per cent Anhydrous methyl alcohol 96.0 Furfuryl alcohol 1.5 Morpholine 1.5 Water 1.0 Example B Anhydrous methyl alcohol 87.5 1,3,5 xylenol 10.0 Morpholine 1.5 Water 1.0 Example C Anhydrous ethyl alcohol 91.2 Morpholine 2.0 Cyclohexanol 2.0 Water 4.8 Emample D Anhydrous methyl alcohol 96.0 Cyclohexanol 1.5 Morpholine 1.5 Water 1.0 Example E Anhydrous methyl alcohol 96.0 Furfuryl alcohol 1.5 Pipyrldine 1.5 Water 1.0

It is to be understood. of course, that thefore- Per cent Anhydrous methyl alcohol 96.0 Furfuryl alcohol 1.5 Morpholine 1.5 Water 1.0

2. A flushing fluid for hydraulic brake systems comprising the following ingredients in approximately the proportions indicated:

Per cent Anhydrous methyl alcohol 87.5 1,3,5 xylenol 10.0 Morpholine 1.5 Water 1.0

3. A flushing fluid for hydraulic brake systems comprising the following ingredients in approximately the proportions indicated:

Per cent Anhydrous ethyl alcohol 91.2 Morpholine 2.0 Cyclohexanol 2.0 Water 4.8

4. A substantially anhydrous flushing fluid for hydraulic brake systems comprising at least 70% of a lower straight chain aliphatic alcohol containing less than 4 carbon atoms, 1-20% of a compound effective to promote solvent action of the alcohol on hydraulic fluid deterioration products and selected from the group consisting of furfuryl alcohol, cyclohexanol, alpha terpinol, benzyl alcohol, thymol, cresol, 1,3,5 xylenol, phenol and catechol, and 1-5% of a compound effective to inhibit corrosion as Well as promote solvent action of said alcohol and selected from the group consisting of morpholine, methyl morpholine, ethyl morpholine, pipyridine, cyclohexylamine, dicyclohexylamine, benzothiazol, pyridine and aniline.

5. A substantially anhydrous flushing fluid for hydraulic brake systems comprising at least 70% of a lower straight chain aliphatic alcohol containing less than 4 carbon atoms, 1-20% of a compound effective to promote solvent action of the alcohol on hydraulic fluid deterioration products and selected from the group consisting of furfuryl alcohol, cyclohexanol, alpha terpinol, benzyl alcohol, thymol, cresol, 1,3,5 xylenol, phenol and catechol, 15% of a compound effective to inhibit corrosion as well as promote solvent action of said alcohol and selected from the group consisting of morpholine, methyl morpholine, ethyl morpholine, pipyridine, cyclohexylamine, dicyclohexylamine, benzothiazol, pyridine and aniline, and not over 2% water.

CHESTER M. WHITE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,903,287 Cox Apr. 4, 1933 2,171,491 Endres Aug. 29, 1939 2,179,999 Fegg Nov. 14, 1939 2,196,152 Kvalnes Apr. 2,1940 2,218,233 Fegg Oct. 15, 1940 

